Hydrocarbons and other fluids are often contained within subterranean formations at elevated pressures. Wells drilled into these formations allow the elevated pressure within the formation to force the fluids to the surface. However, in low pressure formations, or when the formation pressure has diminished, the formation pressure may be insufficient to force the fluids to the surface. In these cases, a positive displacement pump, such as a piston pump, can be installed to provide the required pressure to produce the fluids.
The function of pumping systems in gas wells is to produce liquid, generally water, that enters the wellbore naturally with the gas. This is necessary only on low flow rate gas wells. In high flow rate gas wells, the velocity of the gas is sufficient that it carries the water to surface. In low flow rate wells, the water accumulates in the wellbore and restricts the flow of gas. By pumping out the water, the pump allows the well to flow at a higher gas rate, and this additional produced gas, which eventually is related to additional revenue, pays for the pumping unit.
The use of a retrievable pumping system in a low-flow rate gas well is subject to several economic restrictions. One principal restriction is that the pumping system must be inexpensive to replace, otherwise the cost of installing or replacing the unit overwhelms the additional revenue from an increase in the low flow rate of gas.